Childhood and adolescence include periods of growth in which the pediatrician meets multiple challenges in terms of cooperation, compliance with treatment, and the patient�s family, thus constituting the pedodontic triangle. The importance of long-term patient monitoring should not be neglected, especially for those in the stage of growth and development of temporary or permanent dentition, when a real cascade of bad events can be triggered. Mobile dental appliances with the indication to be worn both day and night, less during meals and when tooth cleaning is taking place. They are used for a relatively short period as part of a wider treatment plan. The efficiency of an orthodontic appliance is appreciated by the possibilities it offers to reach the desired result in a minimum treatment time, without affecting the biological integrity of the substrate on which it operates. Ortodontic mobilisable devices used to correct dento-maxillary abnormalities, requires plates with orthodontic force, retention and anchoring. If these are used as contention devices, is needed only retention. Study group regards the selection, examination and orthodontic treatment of 46 cases at the Orthodontic Clinic of the University of Medicine and Pharmacy T�rgu Mure� between 2014-2016.The study deals with the theoretical aspects regarding biomechanics and the principles of orthodontic treatment and at the same time represents a synthetic exposure characteristics of the orthodontic devices, considering the development of new techniques. Orthodontic treatment begins in childhood, around the age of 6 years old or when the child has 4-6 milk teeth, when we already can see problems in growing of jaw and permanent teeth.